1. Field of the Invention
The present invention relates to a detection apparatus which is used in an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus.
2. Description of the Related Art
In general, the image forming apparatus such as the copying machine, the printer, the facsimile apparatus is provided with a sheet detecting apparatus which detects a timing point at which a sheet passes when the sheet is conveyed as a recording medium.
In the image forming apparatus, the sheet detecting apparatus detects a timing point at which the sheet passes in order to determine jamming, multiple feeding, or the like.
In general, the sheet detecting apparatus is configured to include a rotatable sensor lever and an optical sensor such as a photo interrupter. The sensor lever is applied by a force in a direction abutting onto the sheet, and is rotatably pushed down when the sheet passes through. Therefore, the photo interrupter is operated such that a detection area of the photo interrupter is closed or opened, and thus a leading edge of the passing sheet is detected. Such a type of sheet detecting apparatus, for example, is disclosed in Japanese Patent Laid-Open No. 2008-150149.
However, the sheet detecting apparatus disclosed in Japanese Patent Laid-Open No. 2008-150149 has problems as follows.
When returning to a home position after the sheet passes through, the sensor lever comes into conflict with a stopper which defines the home position of the sensor lever and thus is rebounded. At this time, the sensor lever transects the detection area of the photo interrupter several times, so that a chattering phenomenon that a detection signal generated from the photo interrupter is repeatedly turned on/off may occur.
Specifically, in a case where a plurality of sheets is successively conveyed, when the leading edge of the following sheet is arrived at the sensor lever before the chattering is lessened, the leading edge of the following sheet is not correctly detected.
Therefore, in the related art, a sheet conveying speed and an inter-sheet distance is necessarily set by estimating a time taken for lessening the chattering, so that there is a limitation in increasing the sheet conveying speed and an image forming speed.
The invention has been made in view of the above circumstances, and it is desirable to provide a detection apparatus which prevents an erroneous detection due to the chattering.